State of the Art DC-DC Converter Topologies for the Multi-Terminal DC Grid Applications: A Review

The high power dc-dc converters emerged as the key circuit element for the future multi-terminal dc grid due to rapid increase in the number of HVDC transmission lines. Beside power conversion, it can provide many functionalities such as bidirectional power flow, power flow control and dc fault isolation. Recently, many high power dc-dc converter topologies have been proposed in the literature for applications in the dc grid. The problem with these, however, is that they are not classified in to various categories based on different parameters such as internal isolation, power density or conversion ratio. This review proposes a taxonomy of most efficient state-of-the-art dc-dc converter topologies based on the structural affinities. Most prominent converters are classified in to two major groups based on the internal isolation. Then, the basic structure, operating principle and performance capabilities accompanied by key advantages and major limitations of each converter is discussed. Furthermore, this study highlights the most suitable converter topologies for the application of HVDC grid interconnection.